JPS5843891B2 - Parent-child instrument transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a system protection relay that connects the new winding to a separately wound child winding when dielectric breakdown occurs in the lead wire connecting the new winding, etc., resulting in a short circuit between the new winding terminals. This invention relates to parent-child instrument transformers used to prevent malfunctions of system protection relays due to residual voltage.

FIG. 1 is a diagram illustrating the structure and use of a conventional parent-child instrument transformer.

In the figure, 1 is a primary winding, 2 is a new winding, and 3 is a child winding, and these windings are wound around an iron core 4.

These configurations are conventional parent-child instrument transformers.

5 is a system protection relay (protection Ry
), 6 is a voltage differential relay (differential Ry) that operates when the difference in voltage between the new winding 2 and the child winding 3 exceeds a certain voltage.

Furthermore, the protection Ry 5 and the differential Ry 6 are coordinated in terms of operating time.

7 is a lead wire connecting the new winding 2 and the protection Ry5.

In the configuration shown in FIG. 1, if dielectric breakdown occurs between the F and the leads of the lead wire 7 and a short circuit occurs, the protection RV 5 and the differential Ry 6
The input voltage on the protection Ry 5 side becomes zero.

- Since some voltage remains in the male winding 3, the differential Ry
6 works.

If the operating time of the protection Ry 5 is set to be longer than the operating time of the differential Ry 6, the protection Ry 5 will not operate in the event of a failure not related to the power supply system, such as a secondary lead wire, and the power supply will be interrupted. No more waking up.

In parent-child instrument transformers intended for such uses, as is clear from the above, the differential Ry 6
It is necessary that a residual voltage sufficient to operate the child winding 3 be generated in the child winding 3.

The residual voltage is generated as follows.

That is, an overcurrent flows through the new winding 2 due to a short circuit between the lead wires FF'.

This overcurrent is limited by the leakage impedance of the primary winding 1 and the new winding 2, and at this time, the magnetic flux remaining in the iron core 4 is limited by the overcurrent and the leakage impedance of the new winding 2 (F, F'
(including the lead wire impedance up to the point).

Since this magnetic flux passes through the child winding 3, a voltage corresponding to the magnetic flux is generated in the child winding 3 as a residual voltage.

It is necessary that this residual voltage is large enough to operate the differential Ry 6, but in conventional parent-child type instrument transformers, it is 30 to 50% of the normal voltage of the child winding 3. It is difficult to operate the differential RV at high speeds, and a disadvantage is that a more expensive and highly sensitive differential Ry must be developed and used.

The present invention was made to eliminate this drawback.
It is an object of the present invention to provide a parent-child type instrument transformer in which a conventional inexpensive differential RY can be used.

Next, the present invention will be explained with reference to the embodiment shown in FIG.

As is clear from FIG. 2, the parent-child instrument transformer of the present invention has a secondary winding (new winding) 2 and a coupling winding 10 connected to the iron core 8, and a secondary winding (child winding ) 3 and a coupling winding 11 are wound around an iron core 9, a primary winding 1 is commonly wound around these cores 8 and 9, and coupling windings io and ii are connected.

In addition, the new winding 2 is connected to the protection Ry 5 and the differential Ry 6, and the child winding 3
It is the same as in the conventional case that is connected to the differential Ry6 via a lead wire.

In such a parent-child type instrument transformer, when a predetermined voltage is applied between the terminals of the next winding 1, the iron cores 8 and 9 are excited, generating a total magnetic flux φ in the iron core, and this magnetic flux φ is transferred to the iron core. 8,
9, the magnetic flux in the iron core 8 is distributed to the new winding 2, and the magnetic flux in the iron core 9 is applied to the child winding 3 at a predetermined ratio. is configured to occur.

For example, if the cross-sectional areas of iron cores 8 and 9 are selected equally, then the next winding 1,
The number of turns of parent and child windings 2, 3 and coupling winding 10.11 is set to N1. N2. When N3, a predetermined voltage E is applied to the negative winding 1.
(v t ), the voltage of V2-Vl is applied to the parent and pre-winding 2 wires, respectively, and the iron core 8
.

In this configuration, if a short circuit occurs due to dielectric breakdown between the lead wires 7 and 117 of the new winding 2, an overcurrent will flow through the new winding 2.

This overcurrent decreases the magnetic flux of the iron core 81,
It is eventually supplied from the primary winding 1 via the coupled windings i o , ii.

At this time, the total magnetic flux in the iron cores 8 and 9 becomes equal to the value obtained by dividing the applied voltage ■1 by the leakage impedance of the primary winding 1, the total leakage impedance of the coupling windings io and ii, and the new winding 2. .

The magnitude of this magnetic flux is 40 to 60% of the predetermined applied voltage under normal conditions.
%.

The magnetic flux due to the voltage applied to the secondary winding 1 is small in the iron core 8 because the new winding 2 is short-circuited, and most of it passes through the iron core 9.

Therefore, since the number of turns of the child winding 3 is given so that when the magnetic flux in the iron core 9 is φ/2, a predetermined voltage (■2) is obtained with a predetermined - next page applied voltage (Vl), the new winding When a magnetic flux of 0.4 to 0.6 φ flows in the iron core 9 when the wire terminals are short-circuited, a voltage of 0.8 to 1.2 V2 is generated in the child winding 3.

In other words, when the new winding is short-circuited, a predetermined voltage (■
A residual voltage 0.8 to 1.2 times that of 2) can be obtained.

With a residual voltage of such a magnitude, it is possible to drive the differential Ry with sufficient speed.

FIG. 3 shows another embodiment of the present invention, in which primary winding 1 (see FIG. 2) is wound commonly around iron cores 8 and 9, and primary windings 1 and 1' are wound around iron cores 8 and 9, respectively. These are connected in series to form the primary winding, and if we standardize the transformer in which the primary and secondary windings are wound around each individual core, two of these transformers can be combined when needed. In such cases, the connection can be used to create a parent-child instrument transformer.

FIG. 4 shows still another embodiment of the present invention, in which an auxiliary transformer for a parent-child instrument transformer for a low voltage circuit is manufactured using the configuration shown in FIG. 3 (the configuration shown in FIG. 2 may also be used), and if necessary, Iron core 23, -
Next, by combining with a voltage transformer consisting of secondary windings 21 and 22, a parent-child type voltage transformer can be easily obtained.

Although the above explanation has been made regarding the case where the new winding circuit is short-circuited, in practice, there may also be a short-circuit of the child winding circuit.

It is obvious from the symmetry of the parent and child circuits that similar actions and effects are obtained in this case as well.

As described above, according to the present invention, even if dielectric breakdown occurs in the circuit such as the lead wire of the parent (child) winding and a short circuit occurs, the voltage at the terminals of the child (parent) winding is the same as the normal voltage. , or more residual voltage can be obtained, and the conventionally used differential Ry can be used.

In addition, if the auxiliary transformer for the low voltage circuit is configured as shown in Figs. 2 and 3, the existing instrument transformer can be easily converted into a parent-child instrument transformer. be.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional parent-child instrument transformer, FIG. 2 is a schematic diagram of a parent-child instrument transformer of the present invention, and FIGS.
Each figure is a schematic diagram of a parent-child type voltage transformer showing other embodiments of the present invention. 1... - Secondary winding, 2, 3... Secondary winding (parent, child winding), 10, 11... Combined winding, 4
, 8.9... Iron core, 5... System protection relay,
6... Voltage differential relay.

Claims (1)

[Claims] 1. Two iron cores each having a secondary winding and a coupling winding 7 wound thereon are combined, the respective coupling windings are connected, and a primary winding is commonly wound on both cores, and one of the cores is wound with a secondary winding and a coupling winding 7. A parent-child instrument transformer in which the secondary winding of the iron core is a new winding, and the other secondary winding is a child winding. 2. A parent-child instrument transformer in which two iron cores are each wound with a secondary winding, a secondary winding, and a coupling winding, and each of the secondary windings and coupling windings are connected in series.